In the conventional art, such a contact piece is known, for example, from DE 34 15 743 A1. Therein, a contact arrangement is shown for a vacuum interrupter. The contact arrangement has a stationary contact piece and a movable contact piece which is guided such that it can move in relation to the stationary contact piece, the contact pieces lying with their end faces opposite one another in the axial direction. The contact pieces each comprise a pot-shaped contact carrier, which has a hollow-cylindrical wall section and a base wall, and a contact disk which lies axially opposite the base wall. In order to produce an axial magnetic field, slots are provided in the base wall, the wall section and in the contact disk, and these slots delimit conductor tracks which extend helically, with the result that an azimuthal component is impressed on a current flowing via the contact piece and an axial magnetic field is produced. The contact piece designed in this way is envisaged for installation in a vacuum-operated power breaker which is provided for the purpose of interrupting the current flow in an energy distribution system, for example in the event of a short circuit.
By separating the contact pieces of the contact arrangement of the vacuum-operated power breaker, an arc is drawn between the contacts. The magnetic field produced by the slots counteracts a self-contraction of the arc and contributes to quenching of the arc. Owing to the slots provided in the contact disk, the occurrence of eddy currents in the contact disk is also suppressed. The slots are generally produced by metal-cutting manufacturing techniques such as milling, lathe work, drilling and are mechanically and/or electrochemically burred.
The previously known contact piece has the disadvantage that sharp edges are formed at the rims of the slots when said slots are introduced, and these sharp edges increase the electric field strengths, which are in any case very high in the contact region, by a factor β which may be between 3 and even over 10, depending on the radius of curvature of the edges and the contact spacing. However, high electric field strengths in the contact region have a disadvantageous effect on the dielectric strength of contact arrangements which are fitted with such contact pieces.